Plants for transforming and melting metal charges, of the pre-reduced type or not, are known, which comprise an electric arc furnace suitable to collaborate with a tunnel to transport and pre-heat the scrap. The electric furnace provides at least a container, or hearth, and a covering roof. The electrodes are introduced into the roof through suitable holes.
The transport and pre-heating tunnel cooperates with the electric furnace on one side and, on the other side, both with a scrap loading system and also with a gas removal system. The gases, as disclosed by IT-B-949.145 (dated 1973), are drawn in hot from inside the electric arc furnace and run through the whole tunnel in counter-flow to the scrap. The same document also teaches to provide a hearth that oscillates by means of jacks, in order to provide on each occasion the discharge of the slag or the tapping of the molten metal.
It is also known, for example from IT-B-1009463 (dated 1974), to provide systems that continuously feed the pre-heated metal charge inside the furnace. This document also discloses that the pre-heating of the metal charge occurs inside a cylinder made of refractory material rotating around an axis that is inclined with respect to the horizontal. In this way, the metal charge continually changes its position inside the cylinder so that, by means of the convective motions of the gases emerging from the furnace, a uniform heating of the metal charge is obtained before it is introduced into the furnace.
Document U.S. Pat. No. 3,985,497 (dated 1974) teaches to burn the non-combusted gases deriving from the process of pre-heating the metal charge in order to reduce the polluting emissions into the environment.
Other systems for pre-heating scrap in a tunnel before it is sent to the furnace are shown in U.S. Pat. No. 3,813,209 (dated 1973) and U.S. Pat. No. 4,083,675 (dated 1978).
The document Stahl und Eisen 95 (January 1975) describes a method in which the exhaust gases of an electric arc furnace are conveyed in counter-flow through a pre-heating tunnel where the scrap to be continuously loaded into the furnace is transported. This document also provides that inside the furnace, after tapping, a head of liquid metal is maintained of between 4 and 6 tonnes, in order to guarantee a trouble-free start-up of the subsequent melting.
Document IT-B-1201815 (dated 1986) not only provides a continuous feed of the charge into a furnace through a pre-heating plant, but also provides to blow into the bath carburetion means, de-sulphurizing mixtures, de-oxidants and mixtures for the foamy slag. Apart from this, IT'815 also teaches to provide a ladle handler which picks up the ladle filled with molten steel in the tapping station, in order to feed it directly to the casting zone, so as to function as a connecting element between the melting zone and the continuous casting zone of the molten steel. It also provides an intermediate station for heating the ladles in order to keep the temperature of the molten steel at values suitable for casting.
The patents U.S. Pat. Nos. 4,543,124 and 4,564,388 respectively describe a device and a method for transforming and continuously melting metal. They are substantially characterized in that in all the steps of loading, melting and refining, the electric feed to the furnace is maintained at maximum power, irrespective of the steps in the cycle and the technological characteristics of the material being worked.
It also provides that loading with the material that functions as the charge is also continued during the tapping of the molten metal. It further provides that the tapping of the molten metal is about 50% of the total volume of the molten metal, and that it occurs by inclining the furnace at most up to 15°, without removing the electrodes and keeping the electric power to the electrodes at maximum power.
The patent US-B2-6,155,333 substantially returns to the teaching of IT'815 in achieving an integrated plant with a direct connection between the melting zone and the casting zone by using an intermediate metallurgical container.
The documents described above are indicated only as examples, since the literature on this subject is extremely extensive. However, those operating in this field are well-known for their continuous effort to optimize the various technical and technological aspects of the entire process to transform iron material into molten steel to be sent, for example, for continuous casting. The purposes of this continuous research are to guarantee, at the same time:                optimum quality characteristics of the molten material,        reduced wear and risk of damage to parts and components, and hence reduced need for maintenance and replacement, particularly of the coverings and/or refractory material,        reduced energy consumption for the same amount of molten metal,        reduced cycle times,        lower incidence of the cost of manpower.        
In view of this, and based on long and thorough studies and experiments, Applicant has made significant improvements to existing technologies, including those described in the documents mentioned above, has overcome some disadvantages of the state of the art and embodied the present invention.